President Michael D Higgins said it is "deeply worrying" to observe an emerging trend of the rise of extremist language and politics across Europe.
He was speaking last night at an event in the Mansion House to mark Holocaust Memorial Day, which is today, on the 75th anniversary of the liberation of Auschwitz-Birkenau concentration camp on January 27, 1945.
"Some 75 years on, the vis- ible signs of World War Two have largely been erased from the rebuilt cities and towns of Europe and fewer and fewer Holocaust survivors remain to tell their stories," Mr Higgins said.
"As time continues to pass and we move further away chronologically from that darkest period of history, it becomes even more important to understand the obligation of remembering what led to that barbaric chapter and its consequences and learn from it.
"It would be a grievous error to consign the Holocaust or the lessons that should be learnt from it to a past that was assumed to be no longer relevant."
Mr Higgins said we must preserve sites such as Auschwitz-Birkenau.